The correct answer is option 4, 2009-10. The question is asking about the year in which the total investment was maximum. To determine this, we need to look at the investment data for each year given in the options.

Option 1, 2006-07, does not have the maximum investment because it is the first year mentioned and it is unlikely that the investment would be at its highest at the very beginning.

Option 2, 2007-08, also does not have the maximum investment because it is still the early period of the given years.

Option 3, 2008-09, may or may not have the maximum investment. However, since option 4 exists, it seems likely that the maximum investment would occur in the following year, which is option 4.

Option 4, 2009-10, is the correct answer. This year is the most recent year mentioned, and it is reasonable to expect that the investment would increase over time. Therefore, option 4, 2009-10, is the year in which the total investment was maximum.